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Make lint type_alias_bounds's removal sugg maybe-incorrect if the RHS contains shorthand assoc tys

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This commit is contained in:
León Orell Valerian Liehr 2024-06-16 12:22:12 +02:00
parent fdf8f024ad
commit d67b61637e
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2 changed files with 109 additions and 129 deletions
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91
compiler/rustc_lint/src/builtin.rs
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@ -32,11 +32,10 @@ use crate::{
BuiltinMissingCopyImpl, BuiltinMissingDebugImpl, BuiltinMissingDoc,
BuiltinMutablesTransmutes, BuiltinNoMangleGeneric, BuiltinNonShorthandFieldPatterns,
BuiltinSpecialModuleNameUsed, BuiltinTrivialBounds, BuiltinTypeAliasBounds,
BuiltinTypeAliasParamBoundsSuggestion, BuiltinUngatedAsyncFnTrackCaller,
BuiltinUnpermittedTypeInit, BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub,
BuiltinUnsafe, BuiltinUnstableFeatures, BuiltinUnusedDocComment,
BuiltinUnusedDocCommentSub, BuiltinWhileTrue, InvalidAsmLabel,
TypeAliasBoundsQualifyAssocTysSugg,
BuiltinUngatedAsyncFnTrackCaller, BuiltinUnpermittedTypeInit,
BuiltinUnpermittedTypeInitSub, BuiltinUnreachablePub, BuiltinUnsafe,
BuiltinUnstableFeatures, BuiltinUnusedDocComment, BuiltinUnusedDocCommentSub,
BuiltinWhileTrue, InvalidAsmLabel,
},
EarlyContext, EarlyLintPass, LateContext, LateLintPass, Level, LintContext,
};
@ -1406,9 +1405,23 @@ declare_lint_pass!(
TypeAliasBounds => [TYPE_ALIAS_BOUNDS]
);
impl TypeAliasBounds {
pub(crate) fn affects_object_lifetime_defaults(pred: &hir::WherePredicate<'_>) -> bool {
// Bounds of the form `T: 'a` with `T` type param affect object lifetime defaults.
if let hir::WherePredicate::BoundPredicate(pred) = pred
&& pred.bounds.iter().any(|bound| matches!(bound, hir::GenericBound::Outlives(_)))
&& pred.bound_generic_params.is_empty() // indeed, even if absent from the RHS
&& pred.bounded_ty.as_generic_param().is_some()
{
return true;
}
false
}
}
impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
fn check_item(&mut self, cx: &LateContext<'_>, item: &hir::Item<'_>) {
let hir::ItemKind::TyAlias(hir_ty, generics) = &item.kind else { return };
let hir::ItemKind::TyAlias(hir_ty, generics) = item.kind else { return };
// There must not be a where clause.
if generics.predicates.is_empty() {
@ -1437,7 +1450,6 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
let mut where_spans = Vec::new();
let mut inline_spans = Vec::new();
let mut inline_sugg = Vec::new();
let mut affects_object_lifetime_defaults = false;
for p in generics.predicates {
let span = p.span();
@ -1449,45 +1461,22 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
}
inline_sugg.push((span, String::new()));
}
// FIXME(fmease): Move this into a "diagnostic decorator" for increased laziness
// Bounds of the form `T: 'a` where `T` is a type param of
// the type alias affect object lifetime defaults.
if !affects_object_lifetime_defaults
&& let hir::WherePredicate::BoundPredicate(pred) = p
&& pred.bounds.iter().any(|bound| matches!(bound, hir::GenericBound::Outlives(_)))
&& pred.bound_generic_params.is_empty()
&& let hir::TyKind::Path(hir::QPath::Resolved(None, path)) = pred.bounded_ty.kind
&& let Res::Def(DefKind::TyParam, _) = path.res
{
affects_object_lifetime_defaults = true;
}
}
// FIXME(fmease): Add a disclaimer (in the form of a multi-span note) that the removal of
// type-param-outlives-bounds affects OLDs and explicit object lifetime
// bounds might be required [...].
// FIXME(fmease): The applicability should also depend on the outcome of the HIR walker
// inside of `TypeAliasBoundsQualifyAssocTysSugg`: Whether it found a
// shorthand projection or not.
let applicability = if affects_object_lifetime_defaults {
Applicability::MaybeIncorrect
} else {
Applicability::MachineApplicable
};
let mut qualify_assoc_tys_sugg = Some(TypeAliasBoundsQualifyAssocTysSugg { ty: hir_ty });
let enable_feat_help = cx.tcx.sess.is_nightly_build().then_some(());
let mut ty = Some(hir_ty);
let enable_feat_help = cx.tcx.sess.is_nightly_build();
if let [.., label_sp] = *where_spans {
cx.emit_span_lint(
TYPE_ALIAS_BOUNDS,
where_spans,
BuiltinTypeAliasBounds::WhereClause {
BuiltinTypeAliasBounds {
in_where_clause: true,
label: label_sp,
enable_feat_help,
suggestion: (generics.where_clause_span, applicability),
qualify_assoc_tys_sugg: qualify_assoc_tys_sugg.take(),
suggestions: vec![(generics.where_clause_span, String::new())],
preds: generics.predicates,
ty: ty.take(),
},
);
}
@ -1495,20 +1484,36 @@ impl<'tcx> LateLintPass<'tcx> for TypeAliasBounds {
cx.emit_span_lint(
TYPE_ALIAS_BOUNDS,
inline_spans,
BuiltinTypeAliasBounds::ParamBounds {
BuiltinTypeAliasBounds {
in_where_clause: false,
label: label_sp,
enable_feat_help,
suggestion: BuiltinTypeAliasParamBoundsSuggestion {
suggestions: inline_sugg,
applicability,
},
qualify_assoc_tys_sugg,
suggestions: inline_sugg,
preds: generics.predicates,
ty,
},
);
}
}
}
pub(crate) struct ShorthandAssocTyCollector {
pub(crate) qselves: Vec<Span>,
}
impl hir::intravisit::Visitor<'_> for ShorthandAssocTyCollector {
fn visit_qpath(&mut self, qpath: &hir::QPath<'_>, id: hir::HirId, _: Span) {
// Look for "type-parameter shorthand-associated-types". I.e., paths of the
// form `T::Assoc` with `T` type param. These are reliant on trait bounds.
if let hir::QPath::TypeRelative(qself, _) = qpath
&& qself.as_generic_param().is_some()
{
self.qselves.push(qself.span);
}
hir::intravisit::walk_qpath(self, qpath, id)
}
}
declare_lint! {
/// The `trivial_bounds` lint detects trait bounds that don't depend on
/// any type parameters.